Conventionally, as a method of detecting a running position of a train, a method capable of: accumulating values, each of which is obtained by multiplying the number of wheel rotations obtained from a tachogenerator by a wheel diameter; and obtaining a running distance and calculating a position based on the accumulated running distance while using position information of a ground coil of a train protection device placed on a track as a reference is widely known. Meanwhile, Patent Literature 1 mentioned below discloses a technique capable of calculating a position based on position information of the GPS (Global Positioning System), a yaw angular velocity, and speed information of a tachogenerator, thereby improving positional accuracy.
In Patent Literature 1 mentioned below, when the reception reliability of GPS information is high, an own-train-position detection system calculates a position of the own train based on the GPS information. When the reception reliability of the GPS information is medium, the own-train-position detection system calculates a track curvature based on the yaw angular velocity and the information of the tachogenerator while using the GPS information as the reference and compares this curvature with known track curvature information to identify the position of the own train. When the reception reliability of the GPS information is low, the own-train-position detection system uses the running distance provided by the tachogenerator as the reference and compares the track curvature calculated based on the yaw angular velocity and the speed information with the known track curvature information to identify the position of the own train. The track curvature information is obtained by recording the yaw angular velocity, the speed, and the position information in a preliminary test run, associating the recorded information with the curvature, and storing the associated information.